The instant invention relates to a valve seat structure and assembly adapted for high-pressure applications in gate, ball, globe or plug type valves wherein the assembly in either the preferred or alternate embodiment versions may be utilized as original or retrofit and replacement seats.
Typically, seats for the various types valves mentioned above are made from various pliable and resiliently deformable materials such as rubber and plastics. When one gets into very high-pressure applications, however, such as with reactor vessels where pressures can be on the order of 3,000 psi, and frequently in combination with high-temperature and corrosive or hazardous material environments, the rubber and plastic valve seat seals are both inadequate and unsuitable from the standpoint of both reliability and maintenance.
In an effort to overcome the inherent reliability and maintenance problems in high-pressure applications as described above, valve seats were machined from metal alloy material with some sort of flex-lip structure to enable a close tolerance flex-compressive fit with the screwed down valve plug component, being fabricated from an appropriated metal alloy material chosen to more satisfactorily withstand both the pressure and operational environment conditions to which the valve seat would be subjected. Examples of metal valve seats of the type above-described would be as respectively taught in U.S. Pat. No. 2,726,843 to Evans et al dated Dec. 13, 1955; U.S. Pat. No. 3,504,886 to Hulslander et al dated Apr. 7, 1970; U.S. Pat. No. 4,124,194 to Alvarez et al dated Nov. 7, 1978; and U.S. Pat. No. 4,568,062 to Regitz et al dated Feb. 4, 1986.
In the case of metal valve seats, effective seals between the valve plug face contact surface and the seat contact surface is accomplished by providing machined close-tolerance contact surface fits therebetween, and in operation compressively engaging the valve plug face contact surface against the seat flex-lip contact surface with a sufficient force to cause flex-compressive fit thereby generally providing a leak-tight seal.
Although the metal valve seat with close tolerance to valve plug face flex compressive fit is a reliable and effective means to solve the high-pressure and harsh operational environment valve seal problem, there is the hazard of exerting excessive force on the valve seat flex-lip and thereby deflect the metal alloy material thereof beyond its permanent distortion limit and "spring" the valve seat flex-lip so that it no longer is mechanically capable of providing either a close tolerance or flex-compressive fit.
The valve seat structure and assembly taught by applicant herein provides a new and novel means to overcome the above problem while at the same time effecting a metal valve seat sealing under high-pressure and harsh operational conditions by embodying a system of flex-lip stops which prevent distortion of the flex-lip beyond the permanent distortion limit thereof during valve plug face flex-compressive fit sealing therewith while at the same time utilizing a back-pressure effect of the contained fluid to produce a counter force across the flex-lip to more closely conform the close tolerance fits of valve plug face and valve seal face in establishing and maintaining a leak-tight seal.